Interactions Between Endosymbionts Wolbachia and Rickettsia in Tetranychus turkestani: Cooperation or Antagonism?

Maternally inherited endosymbionts are widespread in arthropods, with multiple symbionts commonly co-existing within a single host, potentially competing for or sharing limited host resources and space. Wolbachia and Rickettsia, two maternally-inherited symbionts in arthropods, can co-infect hosts, yet research on their combined impacts on host reproduction and interaction remains scarce. This study used diverse parthenogenetic backcross and antibiotic screening to ex-plore the reproductive effects of these two symbionts on Tetranychus turkestani. Results showed that single Rickettsia infection induced male-killing in the amphigenesis of T. turkestani, leading to ar-rhenotokous embryo death and fewer offsprings. Single Wolbachia infection induced strong cyto-plasmic incompatibility (CI). During dual infection, CI intensity decreased, as Rickettsia's male-killing antagonized Wolbachia - induced CI. Dual-infected mites had increased oviposition, lower mortality, a higher female-to-male ratio, and more offsprings, thus enhancing T. turkestani's fitness. These findings will be helpful to understand the nature of host-endosymbiont interaction and the potential for evolutionary conflicts, offering insights into their co-evolutionary relationship.